The newest update for mobile and tablet devices (iOS 9.3) includes an optional mode called Night Shift. Once enabled, it gradually removes blue light after sunset by shifting to warmer colors. (Our eyes expect to see red light as it gets darker, so seeing cooler light at night disrupts our sleep, according to the American Medical Association.) Night Shift uses your device's clock and location to detect when the sun is setting. By the time you wake up in the morning, your phone or tablet will switch back to emitting those bright blue rays.